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Alternating Pumps Destroys Your Spare A duplex or a system with two pumps is designed to have a backup or spare pump. When an alternator is in the system, you effectively do not have a spare pump. As the person who has been called to repair these pumps over many years, I have learned that there is very little time to repair pump #1. The alternator has made sure that pump #2 has exactly the same number of cycles and the same number of running hours as pump #1. Usually before pump #1 is repaired, pump #2 has also failed. Alternators were designed to split the number of cycles in half for each pump by switching back and forth between the primary and the secondary pump. This means that a pump that would normally cycle 100 times per day only sees 50 cycles per day because the “spare” pump also cycles 50 times a day. Water towers and hydro tanks should never be used for water storage but only to reduce the cycling of the pump or pumps. Even with very large tanks cycling can still be a problem. More modern pump control systems such as the Cycle Stop Valve completely eliminate the cycling that has been associated with hydro tanks and water towers. The pump produces exactly the same amount of water as is being used by maintaining a constant pressure. (see What Are Cycle Stop Valves and Constant Pressure Valves) When cycling has been eliminated, alternators are no longer needed. The primary pump will last much longer running continuously (24/7) than if allowed to cycle 50 or any number of times per day. The secondary pump does need to be exercised occasionally to prevent bearing failure and to circulate the water in the pump and related piping. By exercising this secondary pump only as much as needed, say five minutes once a week, this secondary pump will still be like brand new if the primary pump fails. Now the secondary pump is a reliable back up. When pump #1 is out for repair, there is no need to worry that pump #2 is working on its last leg. Plenty of time is available to repair pump #1 because, pump #2 has been kept in like new condition instead of matching pump #1 cycle for cycle and hour for hour. When used with a Cycle Stop Valve the secondary pump is simply staggered on at a slightly lower pressure than pump #1. An exercise clock can be used to turn on pump #2 for a few minutes once a week. The Cycle Stop Valve on pump #2 having been set at a lower pressure than the Cycle Stop Valve on pump #1, will only allow this pump to produce 5 GPM for the 5 minutes of run time required by the exercise clock. When this extra 5 GPM is forced into the system from pump #2, the Cycle Stop Valve on pump #1 will simply restrict the output of pump #1 by 5 GPM. When the exercise clock turns off pump #2, the Cycle Stop Valve on pump #1 will automatically increase flow by 5 GPM to again exactly match the demand required by the system. The pressures should be staggered to make pump #2 come on at a slightly lower pressure than pump #1. This insures that if for any reason pump #1 fails, the drop in pressure will automatically start up pump #2. This staggered pressure also insures that during normal operation, if more water is needed than can be supplied by pump #1, the pressure will drop and pump #2 will come on and automatically supply the extra amount of water needed. In other words, if pump #1 is a 100 GPM pump and the system is requiring 110 GPM, pump #2 will be started and the Cycle Stop Valve will make it add 10 GPM to the 100 GPM already coming from pump #1. As long as both pumps are working, this system would be capable of supplying 200 GPM if needed. Alternators were a band aid to help reduce cycling from old style systems that used hydro tanks and water towers. Constant pressure systems do not have rapid cycle problems. The secondary pump can now be a reliable backup because of the elimination of the alternator. |
| Cycle Stop Valves® is a registered trademark. All right reserved unless prior authorization is obtained. Cycle Stop Valves are patented: Patent number 5,988,984 and other patents pending. |
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